Snowplows generally have plow blades which include a moldboard and a trip board. A trip board is a plowing blade pivotally attached beneath the lower edge of a moldboard, and a torsion spring or other biasing device is situated between the moldboard and the trip board to maintain the trip board in a generally coplanar relationship (or other desired relationship) with the moldboard. When the trip board strikes an unyielding obstruction on the roadway (or other surface to be plowed) during plowing, the biasing device surrenders to allow the trip board to pivot backwardly so that the obstruction may pass beneath the trip board. When the plow blade passes over the obstruction, the trip board then pivots back to its original position. The trip board thus eliminates stress and  impact damage to a moldboard of a plow blade by giving way when an obstruction is encountered.
The plow blade (moldboard and trip board) is generally affixed to a reversing table which is in turn (usually) pivotally affixed to a mounting frame. The mounting frame is then removably attached to the plowing vehicle. As the vehicle travels forward, the plow blade may be directed to the right and left via the reversing table pivoting on the mounting frame. A lift arm, which is generally powered by a hydraulic cylinder, is also affixed to the front of the motor vehicle. One or more lifting chains or cables descend from the lift arm to the reversing table. When the lift arm is pivoted upwards, the mounting frame, reversing table and moldboard are all raised upwards, which can allow the plowing vehicle to move forward without having the trip board scrape along the roadway.
In most plows, when the lift arm is fully lowered, the lifting chains/cables are slack and the trip board has its lower edge resting on the ground, with the full weight of the moldboard (and of portions of the reversing table and mounting frame) atop it. The plow is then operated with the moldboard in this state, which cases rapid wear on the trip board. Some plow operators take the time to raise the lift arms to a sufficient degree that the lower edge of the moldboard rides at or very near ground level, but the moldboard is still subject to shock and wear owing to irregularities in the road surface, and owing to the raising and lowering of the moldboard as the plowing vehicle encounters changes in the grade of the road. 